SEMAPHORENE, 1,4-ANTHRACENO[2.2.2]CRYPTAND, A CATION AND SOLVENT PHOTORESPONSIVE SYSTEM

Since 1,4-dialkoxyanthracenes are highly fluorescent and solvatochromi c(2), it was expected that construction of a cryptand anchored on thes e positions, such as 1, would generate a new type of efficient chemose nsor for cation recognition(3). The synthesis of 1 (dubbed Semaphorene ) was achieved and the X-ray structure shows that the mean planes of t he aromatic ring and of the ''diazocrown'' are perpendicular; this con fers to 1 conformational properties constrasting with those of the kno wn 9, 10-anthracenocryptands (1f). Semaphorene was shown to exhibit a large change in dipole moment between the ground state and the singlet excited state (Delta mu approximate to 10 Debye) and a high fluoresce nce quantum yield (0.76-1.00) in a variety of solvents. The fluorescen ce properties of 1 have also been investigated in the presence of prot ons and metal cations. The latter induce large shifts in the maximum w avelength emission and quantum yield. The behavior of Ag+ is of specia l interest, as it displays eta(2) hapticity (not eta(6) as in referenc e 1f) as it is linked to the 2, 3 positions of the anthracene ring. By UV and fluorescence spectrometric titration, binding constants for so me metal cations (Na+, Ba2+, Ag+, Tl+) were determined. Semaphorene wa s not found to be photochemically reactive.